Summary Airway management with Tracheal Intubation (TI) in critically ill children is an important life-saving procedure with known high risks. We identified that 20% of TI are associated with adverse TI associated events (TIAEs) and 14% with severe oxygen desaturation, defined as SpO2<80% for children with baseline SpO2>90% from our multicenter quality improvement (QI) database. Implementation of a multidisciplinary checklist decreased these event rates by 4% since 2013, and current ongoing QI interventions have targeted implementation of apneic oxygenation and video laryngoscopy to further decrease adverse TIAE and oxygen desaturation. However, we have not yet targeted a critical skill: bag mask ventilation (BMV). BMV is performed in more than 95% of critically ill children who undergo TIs. Bag mask ventilation is considered a fundamental resuscitative skill for all pediatric acute care providers, however BMV is difficult to perform in critically ill children due to challenging patient anatomy and physiology. Assessment of the quality and effectiveness of BMV at the bedside is difficult for clinicians, and objective measure of BMV quality has not been developed. Moreover the clinical impact of the quality of BMV needs to be established, especially on vital organ regional oxygen saturation. Our goals for this project are to characterize the quality of BMV delivered to critically ill children and to evaluate the association of quality of BMV on the occurrence of adverse TIAE, severe oxygen desaturation, and brain oxygen desaturation during TI procedures. We have two specific aims to achieve our goals: 1)to characterize key modifiable components of BMV quality during TI procedures in critically ill children using a Respiratory Function Monitor, and 2) to evaluate the association of the quality of BMV with the occurrence of adverse TIAEs, severe oxygen desaturation (defined as SpO2<80%), and brain tissue regional oxygen desaturation (defined as absolute 20% drop). With success, we will characterize the quality of BMV and patient and provider factors associated with BMV quality. We will document the association of BMV quality with important clinical outcomes such as systemic (arterial) oxygen desaturation and brain regional oxygen desaturation. This information will serve as strong preliminary data that will inform a future multicenter interventional trial which will aim for high quality BMV. Ultimately, we will decrease adverse TIAEs and severe oxygen desaturation in critically ill children.